Create EmptyBlochainBranch and make getBestChain return it if there no known best block

Author: Aurélien Richez

src/it/scala/io/iohk/ethereum/sync/RegularSyncItSpec.scala

@@ -124,7 +124,7 @@ class RegularSyncItSpec extends FreeSpecBase with Matchers with BeforeAndAfterAl
       _ <- peer2.importBlocksUntil(30)(IdentityUpdate)
       _ <- peer1.startRegularSync()
       _ <- peer2.startRegularSync()
-      _ <- peer2.addCheckpointedBlock(peer2.blockchainReader.getBestBranch().get.getBlockByNumber(25).get)
+      _ <- peer2.addCheckpointedBlock(peer2.blockchainReader.getBestBranch().getBlockByNumber(25).get)
       _ <- peer2.waitForRegularSyncLoadLastBlock(length)
       _ <- peer1.connectToPeers(Set(peer2.node))
       _ <- peer1.waitForRegularSyncLoadLastBlock(length)
@@ -181,8 +181,8 @@ class RegularSyncItSpec extends FreeSpecBase with Matchers with BeforeAndAfterAl
         )
       )
       (
-        peer1.blockchainReader.getBestBranch().get.getBlockByNumber(blockNumer + 1),
-        peer2.blockchainReader.getBestBranch().get.getBlockByNumber(blockNumer + 1)
+        peer1.blockchainReader.getBestBranch().getBlockByNumber(blockNumer + 1),
+        peer2.blockchainReader.getBestBranch().getBlockByNumber(blockNumer + 1)
       ) match {
         case (Some(blockP1), Some(blockP2)) =>
           assert(peer1.bl.getChainWeightByHash(blockP1.hash) == peer2.bl.getChainWeightByHash(blockP2.hash))

src/it/scala/io/iohk/ethereum/sync/util/RegularSyncItSpecUtils.scala

@@ -187,7 +187,6 @@ object RegularSyncItSpecUtils {
         case Some(bNumber) =>
           blockchainReader
             .getBestBranch()
-            .get
             .getBlockByNumber(bNumber)
             .getOrElse(throw new RuntimeException(s"block by number: $bNumber doesn't exist"))
         case None => blockchainReader.getBestBlock().get

src/it/scala/io/iohk/ethereum/txExecTest/util/DumpChainApp.scala

@@ -103,7 +103,7 @@ object DumpChainApp
   val blockchain: Blockchain = new BlockchainMock(genesisHash)
   val blockchainReader: BlockchainReader = mock[BlockchainReader]
   val bestChain: BlockchainBranch = mock[BlockchainBranch]
-  (blockchainReader.getBestBranch _).expects().anyNumberOfTimes().returning(Some(bestChain))
+  (blockchainReader.getBestBranch _).expects().anyNumberOfTimes().returning(bestChain)
   (bestChain.getHashByBlockNumber _).expects(*).returning(Some(genesisHash))
 
   val nodeStatus: NodeStatus =

src/main/scala/io/iohk/ethereum/consensus/pow/validators/OmmersValidator.scala

@@ -33,7 +33,7 @@ trait OmmersValidator {
     val getNBlocksBack: (ByteString, Int) => List[Block] =
       (_, n) =>
         ((blockNumber - n) until blockNumber).toList
-          .flatMap(nb => bestBranch.flatMap(_.getBlockByNumber(nb)))
+          .flatMap(nb => bestBranch.getBlockByNumber(nb))
 
     validate(parentHash, blockNumber, ommers, getBlockHeaderByHash, getNBlocksBack)
   }

src/main/scala/io/iohk/ethereum/domain/Blockchain.scala

@@ -103,8 +103,7 @@ class BlockchainImpl(
   override def isInChain(hash: ByteString): Boolean =
     (for {
       header <- blockchainReader.getBlockHeaderByHash(hash) if header.number <= blockchainReader.getBestBlockNumber()
-      bestBranch <- blockchainReader.getBestBranch()
-      hash <- bestBranch.getHashByBlockNumber(header.number)
+      hash <- blockchainReader.getBestBranch().getHashByBlockNumber(header.number)
     } yield header.hash == hash).getOrElse(false)
 
   override def getChainWeightByHash(blockhash: ByteString): Option[ChainWeight] = chainWeightStorage.get(blockhash)
@@ -224,7 +223,7 @@ class BlockchainImpl(
     val latestCheckpointNumber = getLatestCheckpointBlockNumber()
 
     val blockNumberMappingUpdates =
-      if (blockchainReader.getBestBranch().flatMap(_.getHashByBlockNumber(block.number)).contains(blockHash))
+      if (blockchainReader.getBestBranch().getHashByBlockNumber(block.number).contains(blockHash))
         removeBlockNumberMapping(block.number)
       else blockNumberMappingStorage.emptyBatchUpdate
 
@@ -293,7 +292,7 @@ class BlockchainImpl(
   ): BigInt =
     if (blockNumberToCheck > 0) {
       val maybePreviousCheckpointBlockNumber = for {
-        currentBlock <- blockchainReader.getBestBranch().flatMap(_.getBlockByNumber(blockNumberToCheck))
+        currentBlock <- blockchainReader.getBestBranch().getBlockByNumber(blockNumberToCheck)
         if currentBlock.hasCheckpoint &&
           currentBlock.number < latestCheckpointBlockNumber
       } yield currentBlock.number

src/main/scala/io/iohk/ethereum/domain/BlockchainReader.scala

@@ -10,6 +10,7 @@ import io.iohk.ethereum.db.storage.ReceiptStorage
 import io.iohk.ethereum.db.storage.StateStorage
 import io.iohk.ethereum.domain.branch.BestBlockchainBranch
 import io.iohk.ethereum.domain.branch.BlockchainBranch
+import io.iohk.ethereum.domain.branch.EmptyBlockchainBranch
 import io.iohk.ethereum.mpt.MptNode
 import io.iohk.ethereum.utils.Logger
 
@@ -70,16 +71,16 @@ class BlockchainReader(
   def getReceiptsByHash(blockhash: ByteString): Option[Seq[Receipt]] = receiptStorage.get(blockhash)
 
   /** get the current best stored branch */
-  // FIXME this should not be an option as we should always have the genesis
-  // but some tests prevent it to simply be BlockchainBranch for now
-  def getBestBranch(): Option[BlockchainBranch] =
-    getBestBlock().map { block =>
-      new BestBlockchainBranch(
-        block.header,
-        blockNumberMappingStorage,
-        this
-      )
-    }
+  def getBestBranch(): BlockchainBranch =
+    getBestBlock()
+      .map { block =>
+        new BestBlockchainBranch(
+          block.header,
+          blockNumberMappingStorage,
+          this
+        )
+      }
+      .getOrElse(EmptyBlockchainBranch)
 
   def getBestBlockNumber(): BigInt = {
     val bestSavedBlockNumber = appStateStorage.getBestBlockNumber()

src/main/scala/io/iohk/ethereum/domain/branch/EmptyBlockchainBranch.scala

@@ -0,0 +1,11 @@
+package io.iohk.ethereum.domain.branch
+import akka.util.ByteString
+
+import io.iohk.ethereum.domain.Block
+
+object EmptyBlockchainBranch extends BlockchainBranch {
+
+  override def getBlockByNumber(number: BigInt): Option[Block] = None
+
+  override def getHashByBlockNumber(number: BigInt): Option[ByteString] = None
+}

src/main/scala/io/iohk/ethereum/jsonrpc/CheckpointingService.scala

@@ -36,7 +36,7 @@ class CheckpointingService(
       req.parentCheckpoint.forall(blockchainReader.getBlockHeaderByHash(_).exists(_.number < blockToReturnNum))
 
     Task {
-      blockchainReader.getBestBranch().flatMap(_.getBlockByNumber(blockToReturnNum))
+      blockchainReader.getBestBranch().getBlockByNumber(blockToReturnNum)
     }.flatMap {
       case Some(b) if isValidParent =>
         Task.now(Right(GetLatestBlockResponse(Some(BlockInfo(b.hash, b.number)))))

src/main/scala/io/iohk/ethereum/jsonrpc/EthProofService.scala

@@ -206,7 +206,7 @@ class EthProofService(
     def getBlock(number: BigInt): Either[JsonRpcError, Block] =
       blockchainReader
         .getBestBranch()
-        .flatMap(_.getBlockByNumber(number))
+        .getBlockByNumber(number)
         .toRight(JsonRpcError.InvalidParams(s"Block $number not found"))
 
     def getLatestBlock(): Either[JsonRpcError, Block] =

src/main/scala/io/iohk/ethereum/jsonrpc/EthTxService.scala

@@ -158,7 +158,7 @@ class EthTxService(
     Task {
       val bestBranch = blockchainReader.getBestBranch()
       val gasPrice = ((bestBlock - blockDifference) to bestBlock)
-        .flatMap(nb => bestBranch.flatMap(_.getBlockByNumber(nb)))
+        .flatMap(nb => bestBranch.getBlockByNumber(nb))
         .flatMap(_.body.transactionList)
         .map(_.tx.gasPrice)
       if (gasPrice.nonEmpty) {

src/main/scala/io/iohk/ethereum/jsonrpc/ResolveBlock.scala

@@ -35,7 +35,7 @@ trait ResolveBlock {
   private def getBlock(number: BigInt): Either[JsonRpcError, Block] =
     blockchainReader
       .getBestBranch()
-      .flatMap(_.getBlockByNumber(number))
+      .getBlockByNumber(number)
       .toRight(JsonRpcError.InvalidParams(s"Block $number not found"))
 
   private def getLatestBlock(): Either[JsonRpcError, Block] =

src/main/scala/io/iohk/ethereum/jsonrpc/TestService.scala

@@ -372,7 +372,7 @@ class TestService(
 
     val blockOpt = request.parameters.blockHashOrNumber
       .fold(
-        number => blockchainReader.getBestBranch().flatMap(_.getBlockByNumber(number)),
+        number => blockchainReader.getBestBranch().getBlockByNumber(number),
         blockHash => blockchainReader.getBlockByHash(blockHash)
       )
 
@@ -412,7 +412,7 @@ class TestService(
 
     val blockOpt = request.parameters.blockHashOrNumber
       .fold(
-        number => blockchainReader.getBestBranch().flatMap(_.getBlockByNumber(number)),
+        number => blockchainReader.getBestBranch().getBlockByNumber(number),
         hash => blockchainReader.getBlockByHash(hash)
       )
 

src/main/scala/io/iohk/ethereum/ledger/BlockImport.scala

@@ -305,7 +305,7 @@ class BlockImport(
   private def removeBlocksUntil(parent: ByteString, fromNumber: BigInt): List[BlockData] = {
     @tailrec
     def removeBlocksUntil(parent: ByteString, fromNumber: BigInt, acc: List[BlockData]): List[BlockData] =
-      blockchainReader.getBestBranch().flatMap(_.getBlockByNumber(fromNumber)) match {
+      blockchainReader.getBestBranch().getBlockByNumber(fromNumber) match {
         case Some(block) if block.header.hash == parent || fromNumber == 0 =>
           acc
 

src/main/scala/io/iohk/ethereum/ledger/BlockValidation.scala

@@ -43,7 +43,7 @@ class BlockValidation(
           val numbers = (block.header.number - remaining) until block.header.number
           val bestBranch = blockchainReader.getBestBranch()
           val blocks =
-            (numbers.toList.flatMap(nb => bestBranch.flatMap(_.getBlockByNumber(nb))) :+ block) ::: queuedBlocks
+            (numbers.toList.flatMap(nb => bestBranch.getBlockByNumber(nb)) :+ block) ::: queuedBlocks
           blocks
       }
     }

src/main/scala/io/iohk/ethereum/ledger/BranchResolution.scala

@@ -75,7 +75,7 @@ class BranchResolution(blockchain: Blockchain, blockchainReader: BlockchainReade
   private def getTopBlocksFromNumber(from: BigInt): List[Block] = {
     val bestBranch = blockchainReader.getBestBranch()
     (from to blockchainReader.getBestBlockNumber())
-      .flatMap(nb => bestBranch.flatMap(_.getBlockByNumber(nb)))
+      .flatMap(nb => bestBranch.getBlockByNumber(nb))
       .toList
   }
 }

src/main/scala/io/iohk/ethereum/testmode/TestEthBlockServiceWrapper.scala

@@ -75,7 +75,7 @@ class TestEthBlockServiceWrapper(
     .getBlockByNumber(request)
     .map(
       _.map { blockByBlockResponse =>
-        val bestBranch = blockchainReader.getBestBranch().get
+        val bestBranch = blockchainReader.getBestBranch()
         val fullBlock = bestBranch.getBlockByNumber(blockByBlockResponse.blockResponse.get.number).get
         BlockByNumberResponse(blockByBlockResponse.blockResponse.map(response => toEthResponse(fullBlock, response)))
       }

src/main/scala/io/iohk/ethereum/transactions/TransactionHistoryService.scala

@@ -33,7 +33,7 @@ class TransactionHistoryService(
     val getLastCheckpoint = Task(blockchain.getLatestCheckpointBlockNumber()).memoizeOnSuccess
     val txnsFromBlocks = Observable
       .from(fromBlocks.reverse)
-      .mapParallelOrdered(10)(blockNr => Task(blockchainReader.getBestBranch().flatMap(_.getBlockByNumber(blockNr))))(
+      .mapParallelOrdered(10)(blockNr => Task(blockchainReader.getBestBranch().getBlockByNumber(blockNr)))(
         OverflowStrategy.Unbounded
       )
       .collect { case Some(block) => block }

src/test/scala/io/iohk/ethereum/consensus/pow/validators/StdOmmersValidatorSpec.scala

@@ -81,7 +81,7 @@ class StdOmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPr
     val getNBlocksBack: (ByteString, Int) => List[Block] =
       (_, n) =>
         ((ommersBlockNumber - n) until ommersBlockNumber).toList
-          .flatMap(nb => blockchainReader.getBestBranch().flatMap(_.getBlockByNumber(nb)))
+          .flatMap(nb => blockchainReader.getBestBranch().getBlockByNumber(nb))
 
     ommersValidator.validateOmmersAncestors(
       ommersBlockParentHash,

src/test/scala/io/iohk/ethereum/domain/BlockchainSpec.scala

@@ -45,7 +45,7 @@ class BlockchainSpec extends AnyFlatSpec with Matchers with ScalaCheckPropertyCh
     val validBlock = Fixtures.Blocks.ValidBlock.block
     blockchainWriter.storeBlock(validBlock).commit()
     blockchain.saveBestKnownBlocks(validBlock.number)
-    val block = blockchainReader.getBestBranch().get.getBlockByNumber(validBlock.header.number)
+    val block = blockchainReader.getBestBranch().getBlockByNumber(validBlock.header.number)
     block.isDefined should ===(true)
     validBlock should ===(block.get)
   }
@@ -70,7 +70,7 @@ class BlockchainSpec extends AnyFlatSpec with Matchers with ScalaCheckPropertyCh
   it should "not return a value if not stored" in new EphemBlockchainTestSetup {
     blockchainReader
       .getBestBranch()
-      .flatMap(_.getBlockByNumber(Fixtures.Blocks.ValidBlock.header.number)) shouldBe None
+      .getBlockByNumber(Fixtures.Blocks.ValidBlock.header.number) shouldBe None
     blockchainReader.getBlockByHash(Fixtures.Blocks.ValidBlock.header.hash) shouldBe None
   }
 

src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingServiceSpec.scala

@@ -187,7 +187,7 @@ class CheckpointingServiceSpec
     val blockchain: BlockchainImpl = mock[BlockchainImpl]
     val blockchainReader: BlockchainReader = mock[BlockchainReader]
     val bestChain: BlockchainBranch = mock[BlockchainBranch]
-    (blockchainReader.getBestBranch _).expects().anyNumberOfTimes().returning(Some(bestChain))
+    (blockchainReader.getBestBranch _).expects().anyNumberOfTimes().returning(bestChain)
     val blockQueue: BlockQueue = mock[BlockQueue]
     val syncController: TestProbe = TestProbe()
     val checkpointBlockGenerator: CheckpointBlockGenerator = new CheckpointBlockGenerator()

src/test/scala/io/iohk/ethereum/ledger/LedgerTestSetup.scala

@@ -415,7 +415,7 @@ trait MockBlockchain extends MockFactory { self: TestSetupWithVmAndValidators =>
   val bestChain: BlockchainBranch = mock[BlockchainBranch]
   override lazy val blockchainReader: BlockchainReader = mock[BlockchainReader]
   override lazy val blockchainWriter: BlockchainWriter = mock[BlockchainWriter]
-  (blockchainReader.getBestBranch _).expects().anyNumberOfTimes().returning(Some(bestChain))
+  (blockchainReader.getBestBranch _).expects().anyNumberOfTimes().returning(bestChain)
   override lazy val blockchain: BlockchainImpl = mock[BlockchainImpl]
   //- cake overrides